Surgical devices are used in various open, endoscopic, and laparoscopic surgeries to manipulate tissue, seal or staple tissue, and/or transect tissue volumes and blood vessels. These devices can include end effectors having opposed jaw members that move relative to one another to grasp tissue therebetween. Certain of these devices also include a cutting mechanism that can be advanced through the grasped tissue to transect it. In some cases, the cutting mechanism can be designed to travel within a track formed in one or both jaw members of the cutting mechanism. Moreover, as the cutting mechanism is advanced along a length of the jaw members, it can apply a compressive force to at least one of the jaw members. This compressive force can be combined with delivery of energy to seal tissue volumes and blood vessels being transected. For example, electrical energy can be applied to the grasped tissue to seal it before tissue transection is completed. Such energy can be delivered by various mono-polar and bi-polar radio frequency (RF) electrodes or other energy delivery structures coupled to the jaw members.
Prior art surgical end effectors often are constructed with opposed, generally symmetrical jaw members. The jaw members may be pivotably coupled to one another and may be configured such that they both move or such that one jaw member moves relative to a stationary jaw member. Each generally symmetrical jaw member can have approximately equal widths and heights to the other, and the widths can be greater than the heights to maximize the size of electrode that can be coupled to the surface of each jaw member on either side of the transecting cutting mechanism path.
One problem associated with prior art end effector design is a lack of sufficient stiffness that can be required or desirable in certain situations. For example, in some cases it can be desirable to seal tissue using electrical or other energy without transecting the tissue using the cutting mechanism. In such a situation, it can be difficult to achieve sufficient tissue compression to create a good seal using only the force provided by a jaw closure mechanism. This is typically not a concern when transecting tissue, as the cutting mechanism can be configured to apply a compressive force to the tissue as it advances down the track formed in the jaw members. Applying energy to the tissue concurrently with this increased compression force can ensure sealing of the tissue.
The inability of a jaw closure mechanism to apply sufficient compression forces to tissue is largely due to insufficient stiffness in the jaw members themselves. In particular, closure mechanisms typically apply force to a proximal end of the jaw members to urge them toward one another, thereby compressing tissue between the jaw members. The jaw members, however, deflect along their lengths moving toward a distal end thereof. As a result, insufficient compressive force may be found at the distal end of the end effector and possibly also closer to the proximal end thereof.
Moreover, when dealing with surgical instruments there is often a need to maximize strength while minimizing size. This can be particularly true for minimally invasive procedures or other operations where access to a surgical site is limited to an opening of a certain size, diameter, etc. As noted above, prior art surgical end effectors are often relatively wide compared to their height in order to maximize the size of any electrode or other energy delivery structure positioned on tissue-facing surfaces of the jaw members. This width can be problematic if the device is required to pass through, for example, a smaller diameter passageway.
Accordingly, there is a need for surgical instruments or devices having end effectors with increased stiffness that permit, for example, imparting greater compressive forces to tissue grasped by jaw members. There is also a need for surgical end effectors that maximize jaw member stiffness and surface area available for mounting electrodes or other energy delivery structures, while minimizing the size of the end effector to facilitate introduction in minimally invasive and other surgical procedures.